The invention relates in particular to a franking machine.
The problem of securing “sensitive” data consisting of franking data or marks arises in the field of franking machines.
In this type of machine, it is essential to secure data generated by a unit for generating franking data and sent to a printer unit (for example a printer) for the data to be printed by a print member, such as a printer cartridge, which includes an ink reservoir provided with a print head.
For example, if the data is not secure, a fraudster can intercept it between the data generating unit and the printer unit, or even within the printer unit itself. Thus when a franking mark of value X should be printed on an envelope, the fraudster can replace that mark by a franking mark of value Y greater than X.
Thus the management unit decrements its counter of franking values delivered to the printer unit by only an amount X when in reality a greater amount has been printed.
Various security methods to prevent this are known to the person skilled in the art.
In particular, encrypting the franking data in the management unit, sending it in encrypted form to the printer unit, and then decrypting it before sending it to the print member is known in the art.
However, this cannot be done with standard connections between the data generating unit and the printer unit.
Furthermore, a method of the above kind does not eliminate the risk of a fraudster intercepting the decrypted data in the printer unit and tampering with it before sending it on to the print member.
To make the securing of franking data more reliable, a dedicated print member could be provided that would include an internal circuit for decrypting data and would be inaccessible from the outside, for example a dedicated inkjet printer cartridge.
A solution of the above kind would require specific development of the print members (for example inkjet cartridges) and would therefore no longer allow the use of products available off the shelf.
A solution of the above kind could even lead to modification of the printer unit (printer) itself.
A solution of the above kind tends to make franking machines more complex.
It would consequently be beneficial to be able to secure the franking data in a franking machine in a simple, inexpensive, and efficient manner.
It would also be beneficial to secure the franking data in a franking machine without calling into question the architecture of existing franking machines, and in particular the printing technology used in the machines.
More generally, outside the context of franking machines, there exists a need for securing sensitive or confidential data coming from a data source external to conventional printing mechanisms that use a printer unit incorporating an inkjet printer cartridge.
The various aspects of the invention stated hereinabove aim to remedy at least one of the drawbacks previously cited.